personality assessment

...empirical validation of an untested measure hopefully designed to measure any personality attribute is not possible, efforts at establishing a less impressive kind of validity (so-called
construct validity) may be pursued. A construct is a theoretical statement concerning some underlying, unobservable aspect of an individual’s characteristics or of his internal state....

...excessively feels anxious. Yet his feelings of anxiety, if any, are not directly observable. Any assumed trait (anxiety, for example) that is held to underlie observable behaviour is called a construct. Since the construct itself is not directly measurable, the adequacy of any test as a measure of anxiety can be gauged only indirectly;
e.g., through evidence for its construct...